Lacking formal education, skills, or experience in a particular field or activity. The untrained worker struggled to keep up with the tasks assigned to him.
Not having been taught or conditioned to perform a specific task or behavior. The untrained dog was difficult to control during the walk.
Not shaped, supported, or directed in growth by training techniques (said of plants, vines, branches, etc.). The untrained vines sprawled wildly over the trellis.